# TCP 代理
# readme

"""
p27
22.7.19
    hexdump函数废了...
    --> https://blog.csdn.net/qq_36906509/article/details/79751548

"""
import sys
import socket
import threading

def server_loop( local_host , local_port , remote_host , remote_port , resceive_first):

    server = socket.socket(socket.AF_INET , socket.SOCK_STREAM)

    try:
        server.bind( ( local_host , local_port) )
    except:
        print("[!!] Failed to listen on %s:%d " % (local_host , local_port))
        print("[!!] Check for other listening sockets or correct permissions.")
        sys.exit(0)

    print("[*] Listening on %s:%d" % (local_host , local_port ))

    server.listen(5)

    while True:
        client_socket , addr = server.accept()

        # 打印出本地连接信息
        print("[==>] Received incoming connection from %s:%d" % (addr[0] , addr[1]))

        # 开启一个线程与远程主机通信
        proxy_thread = threading.Thread(target=proxy_thread,
                                        args=(client_socket,remote_host,remote_port
                                              ,resceive_first))
        proxy_thread.start()

def proxy_handler( client_socket , remote_host , remote_port , receive_first ):
    # 连接远程主机
    remote_socket = socket.socket(socket.AF_INET , socket.SOCK_STREAM)
    remote_socket.connect((remote_host,remote_port))

    # 如果有必要从远程主机接收数据
    if receive_first:
        remote_buffer = receive_from(remote_socket)
        hexdump(remote_buffer)

        # 发送给我们的响应处理
        remote_buffer = response_handler(remote_buffer)

        # 如果我们有数据传递给本地客户端,发送它
        if len(remote_buffer):
            print("[<==] Sending %d bytes to localhost." % len(remote_buffer))
        # 现在我们从本地循环读取数据,发送给远程主机和本地主机
        while True:
            # 从本地获取数据
            local_buffer = receive_from(client_socket)

            if len(local_buffer):
                print("[==>] Received %d bytes from localhost." % len(local_buffer))
                hexdump(local_buffer)

                # 发送给我们的本地请求
                local_buffer = request_handler(local_buffer)

                # 向远程主机发送数据
                remote_socket.send(local_buffer)
                print("[==>] Sent to remote.")

            # 接收响应数据
            remote_buffer = receive_from(remote_socket)

            if len(remote_buffer):

                print("[<==] Received %d bytes from remote." % len(remote_buffer))
                hexdump(remote_buffer)

                # 发送到响应处理函数
                remote_buffer = response_handler(remote_buffer)

                # 将响应发送给本地socket
                client_socket.send(remote_buffer)

                print("[<==] Sent to localhost.")

            # 如果两边都没有数据,关闭连接
            if not len(local_buffer) or not len(remote_buffer):
                client_socket.close()
                remote_socket.close()
                print("[*] No more data. Closing connections.")

                break
def hexdump(src, length=16):
    result = []
    digits = 4 if isinstance(src, str) else 2

    for i in range(0, len(src), length):
        s = src[i:i + length]
        hexa = ' '.join([hex(x)[2:].upper().zfill(digits) for x in s])
        text = ''.join([chr(x) if 0x20 <= x < 0x7F else '.' for x in s])
        result.append("{0:04X}".format(i) + ' '*3 + hexa.ljust(length * (digits + 1)) + ' '*3 + "{0}".format(text))

    return '\n'.join(result)

def receive_from(connection):
    buffer = ""

    # 设置超时时间 ----2
    connection.settimeout(2)

    try:
        # 持续从缓存中读取数据直到没有数据或者超时
        while True:
            data = connection.recv(4096)

            if not data:
                break
            buffer += data
    except:
        pass

    return buffer

# 对目标是远程主机的请求进行修改
def request_handler(buffer):
    # 执行包修改
    return buffer

# 对目标是本地主机的响应进行修改
def response_handler(buffer):
    # 执行包修改
    return buffer

def main():

    if len(sys.argv[1:]) != 5:
        print("Usage: ./proxy.py [localhost] [localport] [remotehost] [remoteport]"
              "[receive_first]")
        print("Example: ./proxy.py 127.0.0.1 9000 10.12.132.1 9000 True")
        sys.exit(0)

    # 设置本地监听参数
    local_host = sys.argv[1]
    local_port = int(sys.argv[2])

    # 设置远程目标
    remote_host = sys.argv[3]
    remote_port = int(sys.argv[4])

    # 告诉代理在发送给远程主机之前连接和接收数据
    receive_first = sys.argv[5]

    if "True" in sys.argv[5]:
        receive_first = True
    else:
        receive_first = False

    # 设置好监听
    server_loop(local_host , local_port , remote_host , remote_port , receive_first)

main()
